Gas removal from electrolytic cells



Sept. 20, 1966 J. szEcHTMAN GAS REMOVAL FROM ELECTROLYTIC CELLS Filed June l, 1965 United States Patent O 3,274,082 GAS REMOVAL FROM ELECTROLYTIC CELLS Joshua Szechtman, deceased, late of Byram, Conn., by Rebecca Szechtman, executrix, Byram, Conn., assignor to Chlormetals Incorporated, a corporation of Dela- Ware Filed June 1, 1965, Ser. No. 460,597 7 Claims. (Cl. 204-60) This application is a continuation in-part application of copending application Serial No. 89,941, tiled February 17, 1961.

This invention relates to the removal of chlorine from an electrolytic cell wherein chlorine is generated as a product of the electrolysis of molten metal chloride salts, and is more particularly concerned with the removal of chlorine under conditions such that its corrosive action upon ordinary steel and iron piping and other equipment is eliminated or minimized.

In the electrolysis of an alkali metal chloride or of an alkaline `earth metal chloride wherein the salt is in molten form, high electrolysis temperatures are employed. For example, molten sodium chloride is suitably electrolyzed at a temperature of 1490 to about 1560 F. (810 to about 850 C.). The entire atmosphere within the cell, including the generated chlorine, is, of course, substantially at this temperature. It is well known that hot chlorine, having a temperature of the order indicated, is extremely corrosive to iron and steel. However, it is also known that this corrosive action of chlorine does not occur when the chlorine is at lower temperatures, e.g., below 500 F. and advantageously below about 300 F., as long as the chlorine is dry. The problem of handling hot chlorine evolved from an electrolytic cell during the electrolysis of a molten chloride has been a serious one in the electrolytic art because there are no known metals or alloys which will withstand the corrosive effect of hot chlorine. The corrosion of metals by hot chlorine not only is expensive because of the replacement cost of the metal parts and the necessary maintenance interruptions to replace corroded parts, but also tends to contaminate the product chlorine, thus necessitating subsequent purication steps in order to obtain high purity chlorine. Accordingly, it has been necessary to manufacture piping and other equipment with the hot chlorine from graphite or ceramics. Equipment made of such materials is relatively fragile compa-red to equipment made of metal.

Furthermore, it is desirable to maintain a molten chloride electrolysis Zone of the cell at a pressure slightly below atmospheric, in order that any leakage of gases be of air into the cell, rather than of chlorine out of'the `cell to the atmosphere. The differential between the pressure in the cell and the atmosphere need not be great, and may be as low as the equivalent of a quarter inch of water. This differential will not occur naturally, and, because of the inevitable pressure drop along the exit conduit provided for the chlorine gas, such a cell would normally and in .the absence of specific design features, operate slightly above the surrounding atmospheric pressure.

It is, accordingly, an object of the present invention to provide a method and a system for supplying chlorine from a high temperature molten metal chloride electrolysis cell at a sufficiently low temperature that the problem of corrosion referred to above are not present and the chlorine can be directly conducted into piping and other equipment formed from ordinary iron and steel.

Another object is to provide a method and apparatus for maintaining the internal pressure in such a cell slightly lower than the surrounding atmospheric pressure.

A further object of this invention is to provide a meth- ICC od and apparatus which serves the combined purposes of cooling the hot product chlorine from a molten metal chloride electrolytic cell to a temperature suiciently low to avoid corrosion of standard carbon steel, and at the same time maintain the internal pressure of the cell below the surrounding atmospheric pressure.

In accordance with the invention, the chlorine, as it is generated during the electrolysis reaction, is conducted through the anodes of the electrolysis cell into the cell cover toward an outlet and, before the chlorine reaches the outlet, it is brought into contact and mixed with cold, substantially pure chlorine from a separate source so that rthe temperature of the resulting mixture is sufficiently low that no danger of significant corrosion exists, i.e. a temperature below 500 F., and without contaminating the product chlorine.

Briefly stated, the process comprises electrolyzing a molten metal chloride salt in a substantially air-tight electrolysis zone maintained at a pressure close to but not execeeding the existing atmospheric pressure and at a temperature sufficient to maintain the metal chloride salt in a molten state, whereby gaseous chlorine is evolved, withdrawing from the electrolysis zone evolved gaseous chlorine at substantially the temperature existing in such zone, mixing or co-mingling the evolved chlorine with a second stream consisting essentially of relatively cold or cool and substantially pure chlorine, and withdrawing vfrom the process the mixed chlorine streams in the gaseous phase at a temperature of less than about 500 F., such second chlorine stream having a greater linear vclocity than the evolved chlorine stream and having sufficient mass, at least twice the mass of `the evolved chlorine stream, and a sufficiently low .temperature to produce a,

temperature in the co-mingled chlorine stream of less than about 500 F. in the absence of any indirect heat exchange involving either the evolved chlorine stream or the mixed chlorine streams. In a preferred embodiment, the Vrelative mass and velocity of the second chlorine stream is regulated to maintain the pressure in the electrolysis zone equal to or slightly less Ithan the existing atmospheric pressure surrounding the electrolytic cell.

In another embodiment, the processcomprises electrolyzing a molten metal chloride salt in a substantially airtight electrolysis zone maintained at a pressure close to but not exceeding atmospheric pressure `and at a temperature sufiicient to maintain the metal chloride salt in a molten state, whereby hot gaseous chlorine is evolved, withdrawing the evolved chlorine from the electrolysis zone at substantially the temperature existing in such zone, imparting a swirling movement to a second stream consisting essentially of relatively cooler and substantially pure chlorine, passing such` swirling cooler chlorine axially into a mixing zone and introducing the evolved hot chlorine laterally into such mixing zone for admixture with the cooler chlorine to form a mixed chlorine stream having a temperature of less than about 500 F., and withdrawing the mixed chlorine stream from the mixing zone.

It is a feature of the invention that chlorine generated in a high temperature electrolysis process can be taken from the electrolysis cell directly into ordinary piping and chlorine-handling equipment without: the necessity for employing equipment formed from special alloys or other corrosion-resisting materials.

Other objects and features of the invention will be readily apparent from the following detailed description of an illustrative embodiment thereof and from the accompanying drawings wherein:

FIG. 1 is a longitudinal sectional View of an electrolytic cell embodying features of the present invention, as seen generally along the line 1 1 of FIG. 2;-

FIG. 2 is a transverse cross-sectional view taken generally along the line 2-2 of FIG. 1; and

FIG. 3 is a detailed view of the cell construction which includes the chlorine outlet wherein the cold chlorine is mixed with the hot chlorine to effect the desired cooling.

Referring to the drawing and more particularly to FIGS. 1 and 2, there is illustrated an electrolytic cell designated generally by the reference numeral 10. It will be understood that the invention is not limited to any specilic cell construction and that it may be embodied in any cell producing chlorine upon electrolysis of the corresponding salt. For example, there may suitably be used the cell described in my U.S. Patent No. 3,104,213. Also particularly suitable for use in connection with this invention is the improved cell shown in the accompanying drawing which embodies all of the advantages of the cell disclosed in such patent and in addition has further advantageous features. The cell body 12 of the cell 10 is formed from metal, and is supported upon an insulating support 14. As seen in FIG. 1, the cell 10 defines a sole surface 15 upon which the liquid cathode 16, e.g., molten lead, is adapted to rest and to iiow from left to right. Thus, the elongated cell body 12 is formed with an elongated channel of which the sole 14 is the bottom and which provides the electrolysis chamber 17. Since the cell is adapted to operate at elevated temperatures for the electrolysis of molten salts, e.g., temperatures on the order of 1l00 to 1600 F., which are suitable for the electrolysis of molten salts, any convenient means for heating the cell body and maintaining it at an elevated temperature may be empoyed. Particularly effective is the heating means shown in the drawing whereing the cell body is formed with a plurality of longitudinally-extending conduits which form a closed circuit with a heater 22 and a pump 24. These conduits are suitably filled with molten lead which is maintained at the desired temperature by the heater and is then circulated through the cell body by means of the pump.

Closing the cell is a cover 30 which extends completely across the cell body and extends from one end of the cell body to the other. This cover is formed from an electrically-conductive material and most suitably is formed from graphite. As seen in FIGS. 1 and 2, the cell body 12 is formed with a continuous circumferentially-extending channel 34 which is adapted to be illed with a fluid which is liquid at cell operating temperatures and most advantageously this fluid is lead and the channel 34 communicates by means of suitable conduits 36 with the circuit which includes the conduits 20, the heater 22 and the pump 24. As seen in FIG. 1, the molten lead circuit is suitably provided with a branch 38 through which the molten lead may be introduced when the cell is being started up, this branch suitably being controlled by a valve 40. Depending from cover 30 into the channel 34 is a circumferential liange 42 which is embedded in the cover 30 and which extends downwardly a sufficient distance that its lower end will be immersed in the liquid 46 contained in the channel 34 in order to form a hydraulic seal. The flange 42 is suitably formed from a material which is a non-conductor of electricity, e.g., a rigid refractory such as silicon carbide with ceramic bond.

The cover 30 directly supports the anodes 50 and such support is effected by means of anode stems 52. While in U.S. Patent No. 3,104,213, I show a conduit for the removal of chlorine generated in the cell during electrolysis, most advantageously, as shown in FIG. 1, provision is made for withdrawing chlorine from the cell through the anodes and through the cover in the manner described in my application Serial No. 22,160 tiled April 14, 1960, now abandoned in favor of la now-pending continuation-in-part application. Thus, as seen in FIGS. 1 and 2, the stems 52 are received in slots 53 and 54 formed in the cover 30 and in the anode blocks 50, respectively, so that these parts are removably interconnected, or the stems may be removably connected only with the cover or only with the anodes, or all parts may be integrally interconnected. The power connections are indicated diagrammatically at 56 and 57, but it will `be understood that `any conventional means may be employed to attach the power conductors, and a particularly suitable system is shown in U.S. Patent No. 3,104,213. As seen in FIGS. 1 and 2, a continuous refractory lining 60 is provided along the entire interior walls of the electrolysis chamber 17 of the cell, the lining 60 serving as an electrical insulator and also as a protector of the walls against chemical attack by the chemical contents within the chamber. Since the cover must be electrically insulated from the body of the cell, because it is a conductor of electrolysis current, an insulating sheet 61 completely overlies the top edges of the walls of the cell body 12, being interrupted only by the flange 42. The exterior of the cell is suitably provided with a tight heat-insulating covering 63 which extends across the top and side surfaces of the cover 30 and over the exterior walls of the cell body 12. The Weight of the cover upon the cell body together with the insulating sheet 61 is generally sufficient, but if a tighter relationship is desired, a plurality of spaced-apart clamps (not shown) can be used to secure the cover to the cell body. Such clamps must, of course, be insulated from the cell body in order to prevent electrical contact between cover 30 and cell body 12. Furthermore, the exterior insulating covering effects not only heat insulation but electrical insulation as well.

Referring again to the anodes, it will be seen that the anode blocks 50, the anode stems or supports 52, and the cover 30 are provided with inter-communicating apertures and channels or passageways through which evolved gas, which will hereafter be referred to as chlorine, is led from the lsite of evolution to a point exteriorly of the cell with minimum contact with contaminating surfaces. Thus, -as shown in FIGS. 1 and 2, each anode block 50 is formed with an interior chamber 65 and a plurality of apertures or ducts 66 extend 'downwardly from this chamber to the bottom active face of the anode. The cover 30 is also formed with an interior chamber 67 and this chamber communicates with the chambers 65 in the yanodes by means of the bore 68 in each anode stem or support 52. The connections between the stems and the cover and between the stems and the anode blocks are suitably gas tight. The cover 30 is formed with an extension conduit 69 which communicates with the cover chamber 67. An auxiliary outlet channel 70, which may be stoppered to prevent ingress of air, may be provided in cover 30 to permit venting of the electrolysis chamber yabove the level of the electrolyte.

The means for introducing a stream of cold, or lrelatively cooler, substantially pure chlorine into the hot chlorine stream issuing from the electrolysis chamber may take any convenient form. It may, for instance, comprise la T-junction or Y-junction with the path of travel of the hot evolved chlorine stream being at an angle to the path of travel of the cooler chlorine stream at the junction of the two streams. In an alternative embodiment, the two chlorine streams are mixed using equipment designed as shown at the upper left of FIGS. 1 and 3. As shown in FIG. 1, there is provided Adirectly within the graphite cover `a jet injector type of gas mixing device having an axiail inlet 72 for the cold chlorine, which is `supplied under positive pressure ffrom any oonvenient source, and a lateral inlet 73 connected to the conduit 69 leading from the cover chamber 67 which communicates with the anode stems and the cover. An Kaxial outlet 75 communicates directly With the outlet channel 76 in the cover which in turn is connected to an outlet channel 77 for leading the mixed chlorine stream away `from the cell.

Any jet injector construction is generally suitable for the purposes of this invention but there is shown in FIG. 3 a jet injector construction which is particularly effective. As seen in FIG. 3, the inlet '72 into which the cold chlorine is introduced is provided with a freely rotatable bladed rotor 78 which rotates in response to the movement of the cold chlorine stream and serves to give it a :swirling movement. The inlet channel tenninates in a converging trusto-conical portion which discharges into an outlet conduit 79 having a converging inle-t portion and a diverging outlet portion. The junction between the converging end of the inlet and the diverging portion of the outlet is found in a chamber 81 communicating directly with the lateral inlet 73. As the cold chlorine stream passes axially through the device, the suction `created draws the hot chlorine into the chamber 81 and eiiects intimate admixture between the two chlorine streams so that the mixed stream has the desired low temperature.

The above-described jet injector construction is most suitably formed from graphite by means of conventionai graphite machining techniques. Suitably, the left hand portion of the cell cover as seen in FIG. 1 is fabricated as a unit with the jet injector construction in it and the entire assembly connected to the remainder of the cover. It will be obvious, however, that other means for associating the jet injector with the cell cover may be ernployed and that chlorine-resistant materials other than graphite may be employed without departing from the invention.

There is thus provided a system which can readily be incorporated into or `associated with the cover of an electrolysis cell to solve effectively the problem of handling hot chlorine in the electrolysis of molten chlorides.

The manner in which the electrolyte and the liquid cathode are introduced into and removed from the cell form no part of the present invention and the manner described in U.S. Patent No. 3,104,213 is particularly suitable especially since it insures against entrance of air oxygen or moisture with the electrolyte and the cathode into the electrolysis chamber. Thus, as seen in FIG. 1, the liquid cathode and the molten electrolyte are introduced at the left-hand end of the cell tbody, the molten xlead being introduced through a conduit 80 and the ellectrolyte bein-g introduced through a conduit 82. The conduit 82 extends upwardly into the electrolysis chamber 17 and discharges through a `self-regulating float valve indicated diagrammatically at 84 of the type described in FIG. 5 of U.S. Patent No. 3,104,213. At the righthand end of the cell body 10, there is provided a transverse wall 88 extending between the side Walls of the cell body and engaged by the cover 30 to define the downstream end of the electrolysis chamber proper and to define an end compartment 89. The cell bottom slopes downwardly in the vicinity of the transverse walls in order to form a well 90 into which the wall can extend to form a liquid seal against passage of the lighter electrolyte into the end compartment as long as the liquid level of the cathode is maintained. The end compartment 89 is formed with an outlet opening 92. A tall cylindrical sleeve 94 is provided with apertures 95 and with a nose 96 normally disposed in outlet opening 92, the cathode level being maintained by the apertures 95 through which the alloy formed in the cell is discharged. The upper end of the sleeve 94 extends into va recess in cover 30 and it may be lifted, e.g. by electromagnetic means, to permit emptying of the cathode from the cell. Suitable electrical insulation (not shown) prevents contact between sleeve 94 and cover 3).

It will be unde-rstood that the quantity of cold chlorine to be introduced for admixture with the hot chlorine generated by the electrolysis reaction land the rate of its introduction will `depend upon the temperature of the cold chlorine and the temperature and rate of evolution of the hot chlorine, as well as the nal temperature desired in the mixture. However, in a given cell operated at a given current density a predetermined quantity of chlorine ti will be evolved per unit time from la given chloride, as is well known to those skilled in the art.

The amount (mass) of cold, substantially pure chlorine used is desirably at least twice, and advantageously four to six times, the mass of the hot evolved chlorine. The amount of cold chlorine, its temperature ,and pressure and its ilinear velocity at the point of mixing with the hot evolved chlorine, the amount and temperature of the hot evolved chlorine, the desired differential between the pressure maintained in the electrolysis zone and existing atmospheric pressure, and the desired temperature of the mixed effluent chlorine stream withdrawn from the process are correlative variables, and it should be understood that one or a plurality of them may be adjusted to achieve satisfactory performance of the process.

The quantity of cold chlorine per unit time is suitably controlled in response to the indications of a thermocouple or other temperature-sensitive device in the mixed chlorine outlet line. In this connection, a valve is suitably provided in the cold chlorine inlet line and this valve is actuated, either manually or automatically, in response to the temperature sensitive device.

In a typical operation, e.g., the electrolysis of molten sodium chloride fed at 15 10 F. at the rate of 12 pounds per minute a current of 150,000 amperes is employed at a voltage of :approximately 4.5 there are evolved 7 pounds of chlorine per minute at 1560" F. To produce a mixed chlorine stream having a temperature of about 300 F., there is introduced through inlet 72 about 41 pounds per minute of substantially pure chloride having a temperature of about 100 F. This produces a 300 F. product chlorine stream of 48 pounds per minute, of which 7 pounds is net production, and the remainder internal recycle chlorine. Indirect heat exchange with conventional carbon steel equipment may be used to cool the 300 F. mixed chlorine stream to a lower temperature if desired.

It will be understood that the cell structure illustrated is a preferred embodiment only and that the invention is not limited to this construction. For example, the chlorine may be evacuated through a single opening in the cell cover communicating with the bottom of the cover as shown in U.S. Patent No. 3,104,213, rather than being evacuatedthrough the anodes. Similarly, the jet injector mixer need not be embedded in the cell cover but may be mounted on the cover with its inlet 73 connected to the chlorine outlet channel of the cover.

It will be understood that various changes and modifications in addition to those indicated above may be made in the embodiments herein described and shown in the drawings without departing from the scope of the invention as defined in the appended claims. It is intended, therefore, that all matter contained in the foregoing description and in the drawings shall be interpreted as illustrative only and not as limitative of the invention.

Having thus described the invention, what is claimed is:

1. A process for producing chlorine which comprises electrolyzing a molten metal chloride salt in a substantially airtight electrolysis zone maintained at a pressure close to but not exceeding the existing atmospheric pressure and at a temperature su'icient to maintain said salt in a molten state, whereby gaseous chlorine is evolved, withdrawing from said zone evolved gaseous chlorine at substantially the temperature existing in said Zone, comingling said evolved gaseous chlorine with a second stream consisting essentially of substantially pure chlorine, said second stream having `a greater linear velocity and at least twice the mass of said evolved chlorine stream, and withdrawing from said process the co-mingled chlorine streams in the gaseous phase at a temperature of less than about 500 F., said second chlorine stream having suicient mass and having a suliciently low temperature relative to said evolved chlorine to produce a temperature in said co-mingled chlorine stream of less than about 500 F. in the absence of any indirect heat exchange,

2. A process for producing chlorine which comprises electrolyzing a molten alkali metal chloride salt in a substantially airtight electrolysis zone maintained at a pressure close to but not exceeding the existing atmospheric pressure and at Ia temperature substantially above 1100 F., sucient to maintain said salt in a molten state, whereby gaseous chlorine is evolved, withdrawing from said zone evolved chlorine at substantially the temperature existing in said Zone, continuously co-mingling said evolved gaseous chlorine with a second stream consisting essentially of substantially pure chlorine, said second stream having a greater linear velocity and at least twice the `mass of said evolved chlorine stream and withdrawing from said process the co-mingled chlorine streams in the gaseous phase at a temperature of less than about 500 F., said second chlorine stream being of sufficient mass and having a sufficiently low temperature relative to said evolved chlorine to produce a temperature in said comingled chlorine stream of less than about 500 F. in the absence of any indirect heat exchange.

3. A process for producing chlorine which comprises electrolyzing molten sodium chloride in a substantially airtight electrolysis zone maintained :at a pressure close to but not exceeding the existing atmospheric .pressure and at a temperature sucient to maintain said sodium chloride in a molten state, whereby gaseous chlorine is evolved, withdrawing from said Zone evolved gaseous chlorine at substantially the temperature existing in said zone, continuously co-mingling said evolved gaseous chlorine with a second stream consisting essentially of substantially pure chlorine, said second stream having a greater linear velocity and at least tive times the mass of said evolved chlorine stream and withdrawing from said process the co-mingled chlorine streams in the gaseous phase at a temperature of less than about 300 F., said second chlorine stream being of suiiicient mass and having a sufficiently low temperature relative to said evolved chlorine to produce :a temperature in said co-mingled chlorine stream of less than about 300 F. in the absence of any indirect heat exchange.

4. A process for producing chlorine which comprises electrolyzing a molten metal chloride salt in a substantially airtight electrolysis Zone maintained at a pressure close to but not exceeding the existing atmospheric pressure and at a temperature sufficient to maintain said salt in a molten state, whereby gaseous chlorine is evolved, withdrawing from said Zone evolved gaseous chlorine at substantially the temperature existing `in said Zone, continuously co-mingling said evolved gaseous chlorine with a second stream consisting essentially of substantially pure chlorine, said second stream having a greater linea-r velocity and at least twice the mass of said evolved chlorine stream, withdrawing from said process the co-mingled chlorine streams in the gaseous phase at a temperature of less than about 500 F., said second chlorine stream being o suliicient mass and having :a suiiciently low temperature relative to said evolved chlorine to produce a temperature in said co-mingled chlorine stream of less than about 500 F. in the absence of any indirect heat exchange, and regulating the relative mass and velocity of said second chlorine stream to maintain the pressure in .said electrolysis Zone so as not to exceed the existing atmospheric pressure.

5. A process for cooling and withdrawing chlorine gas at a temperature of less than about 500 F. from an airtight electrolytic cell having a cover and having an outlet conduit formed in and extending through said cover, and wherein chlorine is evolved by the electrolysis of a molten chlorine-containing electrolyte in a substantially airtight electrolysis zone maintained slightly less than the existing surrounding atmospheric pressure and at a temperature, above about 1000 F., sutiicient to maintain said electrolytic molten, which process comprises withdrawing the evolved chlorine from said electrolysis zone through said outlet conduit of said cell, introducing into `an enlarged mixing Zone -said evolved chlorine and a stream consisting essentially of cooler, substantially pure chlorine, said cooler chlorine being directly injected into and intermingled with said evolved chlorine in said mixing Zone with concurrent iiow of said cooler chlorine and said evolved chlorine to form a mixed chlorine stream having a temperature less than about 500 F., :and withdrawing said mixed chlorine stream from said mixing zone.

6. The process for cooling and withdrawing chlorine gas at a temperature of less than about 500 F. from an airtight electrolytic cell, which process comprises electrolyzing a molten metal chloride salt in a substantially airtight electrolysis Zone maintained at a pressure close to but not exceeding atmospheric pressure and at a temperature suiicient to maintain said salt in a molten state, whereby hot gaseous chlorine is evolved, withdrawing evolved chlorine from said electrolysis zone at substantially the temperature existing in said Zone, imparting a swirling movement to a stream consisting essentially of cooler, substantially pure chlorine, passing said swirling cooler chlorine into a mixing zone and introducing said evolved chlorine laterally into said mixing zone for admixture with said cooler chlorine, -said cooler chlorine being directly injected into and intermingled with said evolved chlorine in said mixing Zone with concurrent flow of said cooler chlorine and said evolved chlorine to form a mixed chlorine stream having a temperature of less than about 500 F. and withdrawing mixed chlorine stream from said mixing zone.

7. The process for cooling and withdrawing chlorine gas at a temperature of less than about 500 F. from an airtight electrolytic cell, which process comprises electrolyZing a molten metal chloride salt in a substantially airtight electrolysis zone maintained at a pressure slightly less than the existing atmospheric pressure and at a temperature suiiicient to maintain said salt in a molten state, whereby hot gaseous chlorine is evolved, withdrawing evolved chlorine from said electrolysis Zone at substantially the temperature existing in said Zone, imparting a swirling movement to a second stream consisting essentially of cooler chlorine, passing said swirling cooler chlorine into a mixing zone and introducing said evolved chlorine laterally into said mixing zone for `admixture with said cooler chlorine, said second stream of chlorine being directly injected into and intermingled with said evolved chlorine in said mixing zone with concurrent flow of said second stream of chlorine and said evolved chlorine to form a mixed chlorine stream, said second chlorine stream having suiiicient mass fand having a sufciently low temperature to produce a temperature in said mixed chlorine stream of less than about 500 F., and withdrawing said mixed chlorine stream from said mixing Zone.

References Cited hy the Examiner UNITED STATES PATENTS 503,429 8/1893 Lyte 204-247 2,860,094 11/1958 Ishizuka 204-164 2,917,441 12/1959 Donald 204-67 JOHN H. MACK, Primary Examiner.

H. WILLIAMS, Assistant Examiner, 

1. A PROCESS FOR PRODUCING CHLORINE WHICH COMPRISES ELECTROLYZING A MOLTEN METAL CHLORIDE SAID IN A SUBSTANTIALLY AIRTIGHT ELECTROLYSIS ZONE MAINTAINED AT A PRESSURE CLOSE TO BUT NOT EXCEEDING THE EXISTING ATMOSPHERIC PRESSURE AND AT A TEMPERATURE SUFFICIENT TO MAINTAIN SAID SALT IN A MOLTEN STATE, WHEREBY GASEOUS CHLORINE IS EVOLVED, WITHDRAWING FROM SAID ZONE EVOLVED GASEOUS CHLORINE AT SUBSTANTIALLY THE TEMPERATURE EXISTING IN SAID ZONE, COMINGLING SAID EVOLVED GASEOUS CHLORINE WITH A SECOND STREAM CONSISTING ESSENTIALLY OF SUBSTANTIALLY PURE CHLORINE, SAID SECOND STREAM HAVING A GREATER LINEAR VELOCITY AND AT LEAST TWICE THE MASS OF SAID EVOLVED CHLORINE STREAM, AND WITHDRAWING FROM SAID PROCESS THE CON-MINGLED CHLORINE STREAMS IN THE GASEOUS PHASE AT A TEMPERATURE OF LESS THAN ABOUT 500*F., SAID SECOND CHLORINE STREAM HAVING SUFFICIENT MASS AND HAVING A SUFFICIENTLY LOW TEMPERATURE RELATIVE TO SAID EVOLVED CHLORINE TO PRODUCE A TEMPERATURE IN SAID CON-MINGLED CHLORINE STREAM OF LESS THAN ABOUT 500*F. IN THE ABSENCE OF ANY INDIRECT HEAT EXCHANGE. 